The first, most expensive phase foresees four resorts with 3,000 rooms each, casinos and leisure infrastructure for an investment of about 6.8 billion euros ($9.2 billion).

When Las Vegas Sands last year chose Madrid over Barcelona to host the project, some observers doubted the company could finance it due to a credit crunch and uncertainties over the Spanish economy.

But Las Vegas Sands chief operating officer Michael Leven said the company was ready to pump in 35-40 percent of the funds for the first phase of the project and had secured financing from banks for the rest.

"That money is available," Leven told a news conference on Friday, without naming the lenders.

Las Vegas Sands is the world's biggest casino company by market value. It is currently subject to a money-laundering investigation by US authorities.

It will build on 750 hectares (1,850 acres) of land in Alcorcon, 15 kilometres (10 miles) southwest of the Spanish capital, said the head of the Madrid regional government Ignacio Gonzalez.

"We expect to lay the first stone at the end of the year," he told the news conference.

"It is the biggest investment that will take place in Spain in the coming years."

The Madrid regional government says it hopes the project will create 200,000 jobs when it is completed.

Spain is currently grappling with an unemployment rate of 26 percent.

The first phase of the project could create around 40,000 direct jobs and another 40,000 indirect ones, Leven said.

"In Singapore, which is about the size of one resort, we employ exactly 10,000 people on our payroll," he said.

Las Vegas Sands operates The Venetian and The Palazzo casinos in Las Vegas and Marina Bay Sands in Singapore, as well as properties in Macao, a former Portuguese colony west of Hong Kong.

The company, run by US billionaire Sheldon Adelson, first unveiled the project six years ago.

The mega-casino project is backed by Spain's ruling conservative Popular Party but is opposed by left-wing parties, labour groups and top officials of the Roman Catholic Church.

Opponents complain that public money will be used for a private project while Spaniards are suffering from cuts in public services.

A protest group, Eurovegas No, said it would demonstrate in Madrid later Friday and would step up its campaign against the project.

"Despite the announcement made today, it is still possible to stop this project with strong mobilisation by citizens," the group, which includes lawyers, architects, environmental associations and others, said in a statement.

Critics fear the casinos will spawn prostitution and crime, and a return to the excesses of Spain's property bubble, which imploded in 2008 triggering a double recession.

Last year the Archbishop of Madrid, Cardinal Antonio Maria Rouco Varela, warned that the casino project carried with it "dangers and risks" for the morals of young people which are "well known".